This invention relates to a method and apparatus for resource scheduling for quality of service (QoS) in telecommunication systems and, more particularly, to a method and apparatus for class based bandwidth scheduling for QoS for CDMA air interfaces.
As wireless communication systems evolve, wireless system design has become increasingly demanding in relation to equipment and performance requirements. Future wireless systems, which will be third and fourth generation (3G and 4G) systems as compared to the first generation analog and second generation digital systems currently in use, will be required to provide high quality high transmission rate data services in addition to high quality voice services systems. The major bottleneck to high quality transmission rate date in 3G systems will be the air interface resource.
The major 3G wireless standards have incorporated requirements for supporting quality of service (QoS) into the relevant specifications. For example, the Universal Mobile Telecommunications System (UMTS) developed by the European Technical Standards Institute (ETSI) and The Japanese Association of Radio Industries and Businesses (ARIB) specifies four QoS classes to be supported. These are defined as conversational, streaming, interactive and background classes. The UMTS system is described in the standard document 3GPP TS 23.107, March 2000, published by ETSI. Other major 3G wireless standards, such as the Telecommunications Industry Association/Electronic Industry Association (TIA/EIA) CDMA2000 standard, and the Chinese TD-SCDMA would also require support for QoS.
Existing QoS schemes for CDMA air interfaces focus on satisfying the needs of specific applications. Typically, they provide QoS guarantees to applications such as voice and best effort service to applications such as packet data. In order to implement efficient QoS schemes on 3G CDMA air interfaces, it is necessary to develop techniques for bandwidth provisioning, scheduling, traffic conditioning etc. These mechanisms need to be optimized for supporting mobile multimedia applications. 3G networks will support a variety of services, including some services that will only be defined in the future. A QoS scheme for 3G must be flexible to allow for adding various services and should also provide means for effective negotiation between a service provider and the end user as far as services subscribed for and provided. The QoS scheme should also be practical in that it should have low complexity for implementation and low volume of control signaling.
The present invention presents a method and apparatus for class based bandwidth scheduling for Quality of Service (QoS) for radio air interfaces. In the method and apparatus, the air interface capacity available for a particular group of users is characterized and then used in a class-based scheduling algorithm to selectively adjust the transmission rates of the users during time frames in which congestion would occur. The method and apparatus may be utilized on either uplink or downlink radio air interfaces.
In an embodiment of the invention, users of an air interface are assigned to at least one of the set of QoS classes xe2x80x9cCxe2x80x9d. The classes may be defined, for example, as conversational class, streaming class, interactive class and background class. Each class xe2x80x9cc∈ Cxe2x80x9d has a total number of users xe2x80x9cNcxe2x80x9d. The classes xe2x80x9ccxe2x80x9d are also each assigned an elasticity xe2x80x9ce(c)xe2x80x9d that assigns a certain delay behavior to the class. The larger the value of elasticity, the larger the delay that may be experienced by users subscribed to the class. Each user xe2x80x9cjxe2x80x9d in a class c has a subscribed rate of data transmission xe2x80x9cro(c,j)xe2x80x9d and an actual rate of data transmission xe2x80x9cro(c,j,t)xe2x80x9d for a time frame xe2x80x9ctxe2x80x9d. Each user xe2x80x9cjxe2x80x9d also has an effective bandwidth xe2x80x9cR(c,j,t)xe2x80x9d for a time frame xe2x80x9ctxe2x80x9d.
According to the embodiment, congestion is determined for each time frame t by determining if the available bandwidth (air interface capacity) is not able to support the effective bandwidth requirements xe2x80x9cR(c,j,t)xe2x80x9d for all users xe2x80x9cjxe2x80x9d of all classes xe2x80x9cc∈ Cxe2x80x9d and, when congestion is determined, the actual rate of data transmission for each user is reduced according to the elasticity xe2x80x9ce(c)xe2x80x9d of the class xe2x80x9ccxe2x80x9d to which the user belongs.